Influence of Compensatory Renal Growth on Susceptibility of Primary Cultures of Renal Cells to Chemically Induced Injury
Advance Access publication September
Influence of Compensatory Renal Growth on Susceptibility of Primary Cultures of Renal Cells to Chemically Induced Injury
Lawrence H. Lash 1 2
David A. Putt 1 2
Rudolfs K. Zalups 0 1
0 Division of Basic Medical Sciences, Mercer University School of Medicine , Macon, Georgia 31207 , USA
1 The Author 2006. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved
2 Department of Pharmacology, Wayne State University School of Medicine , Detroit, Michigan 48201 , USA
Primary cultures of rat renal proximal tubular (PT) and distal
tubular (DT) cells from control and uninephrectomized (NPX)
Sprague-Dawley rats were established to study whether the altered
toxicological responses identified in freshly isolated cells are
maintained in culture. Previous work showed that primary cultures
of PT cells from hypertrophied rat kidneys maintained their
differentiated properties, as evidenced by their high respiratory
rate, active transport function, transport and metabolism of
glutathione, and their hypertrophic phenotype. In the present
study, primary cultures of PT cells from NPX rat kidneys, but to
a much lesser extent DT cells, were more susceptible to cellular
injury induced by either mercuric chloride, KCN, or tert-butyl
hydroperoxide (tBH), than corresponding cells from normal rat
kidneys. Direct comparisons of cytotoxicity and lipid peroxidation
induced by tBH in freshly isolated renal cells showed that the
primary cultures of cells from NPX rat kidneys retained their
altered susceptibility relative to cells from control rats. These
results show that primary cultures of PT cells from NPX rats are
more sensitive to cellular injury induced by three mechanistically
distinct toxicants, demonstrating their usefulness in the study of
the molecular and biochemical basis for the altered phenotype of
compensatory renal growth. This is the first report validating
the use of a mammalian renal cell culture model to study the
toxicological effects of compensatory renal cellular hypertrophy.
Key Words: compensatory renal growth; proximal tubular cells;
primary cell culture; susceptibility; mercuric chloride; oxidative
stress.
Reductions of functional renal mass can occur in humans as
a consequence of renal disease, surgery, or aging. These
reductions in renal mass induce compensatory changes in the
remaining viable nephrons (especially along the proximal
tubule) and are characterized primarily by profound
morphological and functional changes, including increases in cell size,
plasma membrane surface area, single-nephron glomerular
filtration rate, rates of sodium transport, overall protein content,
mitochondrial respiration, and glutathione (GSH) transport and
metabolism
(Harris et al., 1988; Lash and Zalups, 1994; Lash
et al., 2001a,b; Meyer et al., 1996; Nath et al., 1990; Zalups
and Lash, 1990)
. Uninephrectomized (NPX) rats have been
commonly used as a model to study compensatory renal
growth. The acute hemodynamic, functional, and biochemical
effects associated with reduced renal mass and compensatory
growth are nearly complete in rats within 7–10 days
postnephrectomy and are maintained for at least 30 days thereafter
(Meyer et al., 1996; Shirley and Walter, 1991; Zalups et al.,
1987)
. Although varied changes occur throughout the nephron,
the most prominent changes occur in the proximal tubular (PT)
region
(Meyer et al., 1996; Shirley and Walter, 1991)
.
Compensatory renal cellular hypertrophy also has
toxicological implications. Several studies have shown that NPX rats
exhibit altered susceptibility (increased in most cases) to renal
cellular dysfunction and injury induced by a variety of
nephrotoxicants, including inorganic mercury (Hg2þ)
(Zalups,
1997, 2000; Zalups and Diamond, 1987; Zalups and Lash,
1994)
, analgesics
(Henry et al., 1983; Molland, 1976)
, and
cadmium-metallothionein
(Zalups et al., 1992)
. Despite the
wealth of literature showing associations between toxicity and
various cellular processes that are altered by compensatory
renal growth, detailed mechanisms explaining altered
susceptibility to nephrotoxicants are lacking.
To study the biochemical and toxicological impact of
uninephrectomy and compensatory renal growth in the rat
kidney, we previously used suspensions of freshly isolated renal
PT cells from NPX rats as an in vitro model system
(Lash and
Zalups, 1992, 1994)
. Suspensions of isolated distal tubular (DT)
cells were also used as an alternative renal cell population that
is not influenced by compensatory renal growth to the same
degree as PT cells. Our previous findings show that PT cells
from NPX rats retain their hypertrophied phenotype upon
isolation and exhibit (relative to PT cells from control rats)
increased cell size, GSH content, rates of GSH transport and
metabolism, mitochondrial oxidative phosphorylation, and
sensitivity to cytotoxicity induced by Hg2þ
(Lash and Zalups,
1992, 1994)
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